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Comment by majke | Hacker News Reader

That's not how it works. The process of reading your retina / fingerprint is error prone. You can't take hash out of error-prone data blob!

My understanding is that matching the pre-saved template against a fresh scan is a process similar to measuring Levenshtein distance. There is some threshold, and sample with smaller error are accepted. This does imply that the iphone has somewhere stored your _unencrypted_, _unhashed_ template of your fingerprint.

But this is not my area of expertise. Perhaps a subject matter expert can comment.

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Not cryptographic hashing functions, definitely. What about locality-sensitive hashing?

https://en.wikipedia.org/wiki/Locality-sensitive_hashing

I'm not an expert, but I remember getting an impression of a very principled approach to biometrics from John Daugman. This article is about iris recognition and I'm pretty sure it is worth posting in this context: https://www.cl.cam.ac.uk/~jgd1000/csvt.pdf

Indeed it is, inside a sensor (that's why so much trouble replacing one on iphone), gladly raw data never leaves it (same goes for Android as well, except really really old versions, like 4-)

"data never leaves it" reference please?

https://www.apple.com/business/docs/iOS_Security_Guide.pdf

You're looking for the bit on the "Secure Enclave".

https://www.apple.com/business/docs/iOS_Security_Guide.pdf

Find the section titled "Secure Enclave." When the SE needs to store data on the filesystem, it's encrypted with a key that never leaves the SE. Effectively, assuming the encryption is implemented correctly, data 'owned' by the SE is never available to any other part of the system.

Yeah, pretty much. It compares the minutiae[1] from the new scan against that from one, or multiple saved scans from registration.

[1]https://www.wikiwand.com/en/Minutiae

I addressed this when this study was discussed last week, but it's worth reminding that minutiae comparing is not the only technique used for fingerprint matching. [1]

(possible corporate bias) [1] https://corporate.fingerprints.com/en/newsroom/faq-regarding...

Thanks for the link! Yes there are many ways, I always thought minutiae was most common/simplest. There are some interesting advancements also occuring in the optical tomography. [1]

http://ieeexplore.ieee.org/document/7110228/?reload=true

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